Hi. is the dicoloration persisting? or is it changing color? If its changing color, its most likely hematoma. There is nothing to worry about hematoma. But, if its persisting, it could be hypertrophic scar. Hypertrophic scar is like abnormal response to trauma or boils. Can you recall any trauma or boil prior to this lesion? For confirmation, you might need histopathology where a tiny bit of skin is removed and processed for examination under microscope. Both mammogram and ultrasound can give some idea about nature of swelling. As you are already planned for mammogram and ultrasound, i suggest you get this done. If anything suspicious, one might consider histopathology for confirmation. Hope it answers your queries